Defective adenosylcobalamin synthesis in a case of transcobalamin II deficiency.

Cobalamin metabolism has been investigated in a new case of transcobalamin II (TC II) deficiency. Using the chromatobioautographic technique, an abnormal distribution of cobalamins was detected in the child's erythrocytes and reduced synthesis of adenosylcobalamin but not of methylcobalamin in cultured fibroblasts. These results suggest that there may be a close link between TC II-mediated cobalamin transport and intracellular synthesis of adenosylcobalamin (Ado-Cbl).